Used oil products, generally considered as bothersome wastes, represent considerable tonnage in various fields of use such as, for example: oils obtained from draining engines and transmissions of various vehicles, oils obtained from mechanical machines or electric devices, various industrial oils, liquid or semifluid wastes of fatty bodies, etc.
At present, most of these oil wastes are either burned or subjected to various regeneration treatments. For example, according to a known process, the dirty oil is dehydrated by heating it at a temperature of about 150.degree.-160 .degree. C., then subjecting it to treatment with concentrated sulfuric acid. After filtering and heating the dirty oil at about 300.degree. C., two products are obtained. One is regenerated oil of the VEDOL or other type and the other is a blackish muddy residue called "acid mud", the volume of which represents at least 30% of the recovered product after sulfuric acid treatment.
These prior art processes of regenerating dirty oils require the use of several treatment phases and the use of costly and/or dangerous products, such as for example, sulfuric acid in the technique mentioned above.